Introduced flag OfficialCSFMLForWindows

The official CSFML distribution for Windows (available at http://www.sfml-dev.org/download/csfml/ ) adds a "-2" suffix to dll names.

Adding this flag it should be possible to use such distribution without the need to install either VisualStudio or CMake.

Just download and extract into different folders SFML and CSFML from http://www.sfml-dev.org/ (mingw version). Then use --extra-lib-dirs= to add the **bin** of such new folders (twice, one  --extra-lib-dirs= for each folder) and --extra-include-dirs= to add the include dirs.